Analysis of Nonlinear Modal Damping due to Friction at Blade Roots Using High-Fidelity Modelling

2018 ◽  
Author(s):  
Junjie Chen ◽  
Chaoping Zang ◽  
Biao Zhou ◽  
E. P. Petrov
Keyword(s):  
Finite Element ◽  
Direct Calculation ◽  
Surface Friction ◽  
Mode Shapes ◽  
Finite Element Models ◽  
High Fidelity ◽  
Three Dimension ◽  
Blade Vibration ◽  
Modal Damping ◽  
Energy Dissipated

In this paper, a methodology is developed for analysis of modal damping in root joints of bladed discs using large finite element models and detailed description of friction contacts at contact interfaces of the joints. The methods allows the analysis of: (i) a single blade vibration and (ii) a bladed-disc assembly for any family of modes (lower and higher modes) calculating the modal damping factors for different levels of vibrations. Three-dimension solid finite element models are used in the calculations. The analysis is performed in time domain through the transient dynamics analysis. The methodology allows the use of widely available finite element packages and based on the direct calculation of the energy dissipated at root joints due to micro-slip over the multitude of contact elements modelling the surface-to-surface friction contact interactions. The numerical studies of the dependency of modal damping factors on the vibration amplitudes are performed for simplified and realistic bladed disc models for different blade mode shapes, engine-order excitation numbers and nodal diameter numbers using high-fidelity models.

scholarly journals High-fidelity calculation of modal damping caused by friction at blade roots for single blades and tuned bladed disc assemblies

2020 ◽  
pp. 095440622093514
Author(s):  
Junjie Chen ◽  
Chaoping Zang ◽  
Biao Zhou ◽  
EP Petrov
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Direct Calculation ◽  
Surface Friction ◽  
Numerical Studies ◽  
Modal Damping ◽  
Dimensional Finite Element ◽  
Interface Parameters ◽  
Energy Dissipated ◽  
Three Dimensional Finite Element

A method for the analysis of amplitude-dependent modal damping factors is developed for the cases when the energy dissipation is caused by the micro-slip motion at friction contacts of blade root joints. The modal damping at root joints for a lone blade and for tuned bladed disc assemblies is studied. Large three-dimensional finite element models and detailed description of friction contacts by surface-to-surface friction contact elements at contact interfaces of the root joints are used for the calculations. The method allows using available finite element packages and is based on the direct calculation of the energy dissipated at root joints for prescribed levels of vibration amplitudes. The method takes into account the nonlinear dependency of the modal damping factors on the vibration level. The numerical studies of the dependency of modal damping factors on the vibration amplitudes, rotation speed, and contact interface parameters are performed for different families of modes and different nodal diameter numbers.

scholarly journals High-Fidelity Sensitivity Analysis of Modal Properties of Mistuned Bladed Disks Regarding Material Anisotropy

2018 ◽  
Author(s):  
Adam Koscso ◽  
Guido Dhondt ◽  
E. P. Petrov
Keyword(s):  
Sensitivity Analysis ◽  
Finite Element ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Finite Element Models ◽  
Coordinate Systems ◽  
Bladed Disks ◽  
Bladed Disk ◽  
Material Orientation

A new method has been developed for sensitivity calculations of modal characteristics of bladed disks made of anisotropic materials. The method allows the determination of the sensitivity of the natural frequencies and mode shapes of mistuned bladed disks with respect to anisotropy angles that define the crystal orientation of the monocrystalline blades using full-scale finite element models. An enhanced method is proposed to provide high accuracy for the sensitivity analysis of mode shapes. An approach has also been developed for transforming the modal sensitivities to coordinate systems used in industry for description of the blade anisotropy orientations. The capabilities of the developed methods are demonstrated on examples of a single blade and a mistuned realistic bladed disk finite element models. The modal sensitivity of mistuned bladed disks to anisotropic material orientation is thoroughly studied.

Damping Frame Vibrations Using Anechoic Stubs: Analysis Using an Exact Wave-based Approach

2020 ◽  
pp. 1-21
Author(s):  
Hangyuan Lv ◽  
Michael Leamy
Keyword(s):  
Finite Element ◽  
Finite Difference ◽  
Forced Vibration ◽  
Mode Shapes ◽  
Frame Structures ◽  
Vibration Modes ◽  
Timoshenko Beams ◽  
Modal Damping ◽  
Reflection Matrix ◽  
Resonance Response

Abstract This paper explores the addition of small stubs with anechoic terminations (termed herein ‘anechoic stubs’) as means for damping and/or removing vibration modes from planar frame structures. Due to the difficulties associated with representing anechoic boundary conditions in more traditional analysis approaches (e.g., analytical, finite element, finite difference, finite volume, etc.), the paper employs and further develops an exact wave-based approach, incorporating Timoshenko beams, in which ideal and non-ideal anechoic terminations are simply represented by a reflection matrix. Several numerically-evaluated examples are presented documenting novel effects anechoic stubs have on the vibration modes of a two-story frame, such as eliminated, inserted and exchanged mode shapes. Modal damping ratios are also computed as a function of the location and number of anechoic stubs, illustrating optimal locations and optimal reflection ratios as a function of mode number. Forced vibration studies are then carried-out, demonstrating reduced, eliminated, and inserted resonance response.

Anechoic Stubs As a Means for Damping Frame Vibrations: Analysis Using an Exact Wave-Based Approach

2020 ◽  
Author(s):  
Hangyuan Lv ◽  
Michael J. Leamy
Keyword(s):  
Finite Element ◽  
Finite Difference ◽  
Forced Vibration ◽  
Mode Shapes ◽  
Frame Structures ◽  
Vibration Modes ◽  
Timoshenko Beams ◽  
Modal Damping ◽  
Reflection Matrix ◽  
Resonance Response

Abstract This paper explores the addition of small stubs with anechoic terminations (termed herein ‘anechoic stubs’) as means for damping and/or removing vibration modes from planar frame structures. Due to the difficulties associated with representing anechoic boundary conditions in more traditional analysis approaches (e.g., analytical, finite element, finite difference, finite volume, etc.), the paper employs an exact wave-based approach, incorporating Timoshenko beams, in which an anechoic boundary is simply represented by a zero reflection matrix. Several numerically-evaluated examples are presented documenting novel effects anechoic stubs have on the vibration modes of a two-story frame, such as eliminated, inserted and exchanged mode shapes. Modal damping ratios are also computed as a function of the location and number of anechoic stubs, illustrating optimal locations as a function of mode number. Forced vibration studies are then carried-out, demonstrating reduced, eliminated, and inserted resonance response.

scholarly journals Vibration Measurement of Rotating Blades Using a Root Embedded PZT Sensor

2008 ◽  
Vol 15 (5) ◽  
pp. 517-541 ◽  
Author(s):  
M. Sunar ◽  
B.O. Al-Bedoor
Keyword(s):  
Finite Element ◽  
Experimental Studies ◽  
Vibration Measurement ◽  
Mode Shapes ◽  
Rotating System ◽  
Blade Vibration ◽  
Wide Range ◽  
Finite Element Package ◽  
Steady State Responses ◽  
State Responses

Finite element and experimental studies are carried out to test the suitability of a piezoelectric (PZT) sensor in measuring vibrations of blades modeled as beams. The rotating system contains twelve blades mounted to the shaft through a rotor. The PZT sensor is secured in the root between the rotor and blade. First, finite element results are obtained using the finite element package ANSYS. A modal analysis is performed on the system to identify modes and mode shapes. Transient, harmonic and steady-state responses are then computed to test the ability of the PZT sensor in generating signals for blade vibrations. For the experimental part, the blade vibration signals are produced using the PZT sensor and a strain-gage, and the outputs are compared with each other. From both the finite element and experimental results, it is concluded that the root-embedded PZT sensor can be effectively used for blade vibration measurements in a wide range of cases.

scholarly journals Dynamic Response Of Tower Structures

2015 ◽  
Vol 2 ◽  
pp. 85
Author(s):  
Liga Gaile ◽  
Ivars Radinsh
Keyword(s):  
Finite Element ◽  
Structural Changes ◽  
Natural Frequencies ◽  
Resonance Effect ◽  
Dynamic Loads ◽  
Mode Shapes ◽  
Finite Element Models ◽  
Dynamic Parameters ◽  
Vibration Level ◽  
Tower Structure

The present study focuses on the tower type structures response to the dynamic loads. The study analyzes the possible mode shapes regarding to tower structure. The estimation of mode shapes and their dependence from structural changes was made for an existing tower structure. To get an acceptable tower’s vibration level and avoid possibility of resonance effect from usual serviceability loads it was evaluated options to change natural frequencies of the structure. It is performed existing 36m high sightseeing tower dynamic analysis and proposed potential solutions to increase critical natural frequencies of the structure. In this study to obtain dynamic parameters of the sightseeing tower structure have been used finite element models and calculation techniques.

scholarly journals Finite Element Modelling of Laser Stitch Welding Joints for Structural Dynamic Predictions

2019 ◽  
Vol 16 (2) ◽  
pp. 6556-6567
Author(s):  
M. A. S. Aziz Shah ◽  
M. A. Yunus ◽  
M. N. Abdul Rani ◽  
M. S. Mohd Zin ◽  
W. I. I. Wan Iskandar Mirza
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Dynamic Behaviour ◽  
Welding Process ◽  
Shell Element ◽  
High Strength ◽  
Mode Shapes ◽  
Finite Element Models ◽  
Structural Dynamic ◽  
Welded Structure

Laser stitch welding is a joining technique that has been increasingly popular in automotive industries, such as in the manufacturing and assembling of the car’s body-in-white (BiW) due to its advantages over the resistance spot weld, such as low heat application and high strength weld. The dynamic behaviour of a laser stitch welded structure is relatively difficult to predict accurately due to local parameters being induced during the laser welding process, such as heat affected zone (HAZ) and residual stress in the welded structure. This paper presents the idea of modelling the laser stitch weld by investigating different types of element connectors that can be used to represent laser stitch weld, such as rigid body element (RBE2), shell element (CQUAD4), bar element (CBAR) and area contact model (ACM2) format of element connectors. The accuracy of finite element models of laser stitch welded joints is compared in terms of natural frequencies and mode shapes with the experiment counterparts. The dynamic behaviour of the measured structure is obtained by using an impact hammer with free-free boundary conditions. It is found that the accuracy of the finite element models of the laser stitch welded structure highly depends on the involvement of residual stress and the heat affected zones that are generated from the welding process.

Validation of Predictions of Wire Stress of Flexible Pipe With Damaged Tensile Armor Wires Under Combined Tension and Bending

2020 ◽  
Author(s):  
Krassimir Doynov ◽  
Gabriel Rombado ◽  
Nathan Cooke ◽  
Arya Majed
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Finite Element Models ◽  
High Fidelity ◽  
Efficient Computation ◽  
Flexible Pipe ◽  
Irregular Wave ◽  
Numerical Predictions ◽  
Dynamic Substructuring ◽  
Stress Concentration Factors

Abstract The nonlinear kinematic response of a damaged 2.5” flexible pipe under combined tensile and bending cyclic loads is simulated and compared to experimental results. High fidelity finite element model substructures are constructed for intact and broken outer and inner armor wire configurations and assembled in a nonlinear dynamic substructuring (NDS) framework to efficiently simulate the full-scale test configurations. Overall, 12 analysis configurations involving all intact wires, up to 4 broken outer wires, and 2 and 4 broken inner wires combined with 4 broken outer wires are constructed. Each analysis configuration is first preloaded axially and then subject to multiple cycles of (i) pure tension and (ii) combined tension and bending. For each case, tensile armor wire strains are extracted from the simulations and compared to strain measurements from the test. For all cases, numerical predictions and test measurements agree well accurately capturing the redistribution of strains into the adjacent intact wires which result in stress concentration factors. This comprehensive demonstration of accurate capture of flexible pipe damaged wire kinematics by high fidelity finite element models and nonlinear simulations has direct applications to flexible pipe integrity management and remnant life assessments. Given that the NDS framework allows highly efficient computation, it is now feasible to execute real-time irregular wave local fatigue simulations with finite element models that include damaged wire data from physical inspections to more accurately predict remnant life.

Vibro-Acoustic Studies of Transmission Casing Structures

1998 ◽  
Author(s):  
D. Crimaldi ◽  
R. Singh
Keyword(s):  
Finite Element ◽  
Free Boundary ◽  
Boundary Conditions ◽  
Material Properties ◽  
Acoustic Radiation ◽  
Real Life ◽  
Cover Plate ◽  
Mode Shapes ◽  
Finite Element Models ◽  
Free Boundary Conditions

Abstract Automotive transmission casing plates of irregular shape, with complex boundary conditions and non-uniform material properties, are experimentally and computationally studied to acquire a fundamental understanding of their dynamic and acoustic radiation characteristics. A modified flat cover is designed which simplifies the geometry while providing uniform thickness and material properties. Both covers (“real-life” and “laboratory”) are studied with free and bolted boundary conditions. In particular, the free boundary conditions are useful because they eliminate the cover-housing interaction allowing for a more detailed analysis of the cover plate. Finite element models for both covers under the free boundary conditions are developed and refined. Predicted natural frequencies and mode shapes are in excellent agreement with measured modal data. Then the finite element models are coupled with boundary element models to predict acoustic radiation properties. Predictions match well with measured acoustic directivity at resonant frequencies.

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